Tag Archives: condition monitoring

Cylinder Oil Feed Rate – Current Low Load Advice

The main engine manufacturers acknowledge that low load ops are leading to a required change in cylinder lube oil management. It is now no longer the simple act of balancing fuel sulphur with Base Number  and feed rate. The load and relative temperature of the liner will require monitoring to ensure that conditions are avoided which can cause cold corrosion.

RTM 0072 ST Preliminary report


Honing marks removed due to corrosion


In addition the modern lower BN products may not be ideal in all circumstances  – I recommend a thorough review of the CLO management process when working a low load operational policy.

Files are attached for convenience

Wartsila CLO low load RT-148

Wartsila Lubes RT-138

MAN Diesel and Turbo SL2013-571

CLO feed rate optimising proc 2013-05-31


Smart CBM

More and more CBM activities in shipping mean that the industry is finally starting to move!

Not all scavenge drain oil analyses are the same

I can report that not all scavenge drain oil analyses are the same. There are many approaches and the end user needs to be specify the right approach.

Scavenge Drain or Used Cylinder Oil analysis cannot be viewed as a conventional lube oil sample. There are a great many variables that have to be accounted for and normalised before any diagnosis can be made.

Firstly there is no sump so there is a need to understand the relevance of the results to the engine condition at the time of sampling. Therefore feed rate and engine conditions need to be known RPM, %MCR, coolant and scavenge air temperatures, relative humidity and air intake temperatures. These factors at a minimum will indicate the likely conditions that the CLO will experience in terms of dwell time on the liner wall and exposure to water laden air. Both are factors in determination of the potential for corrosive conditions being present.

To get this information you require accurate power information as the feed rate will be normally calculated using grams per kWh, also power loss due to weather, hull condition rudder angle will impact upon the power to rpm relationship. Knowledge of the fuel quality during sampling allows you to understand what abrasive materials may be present and to what degree the presence of unburned or partially pyrolised fuel has on the lubricating qualilty and the determination of BN and viscosity values.

Clearly this information is not required by all analysis providers – FOBAS Engine provided by Lloyd’s Register, a service which I lead, is one service which considers the holistic view in this way – noting that FOBAS Engine has a wider remit for engine performance optimisation and training and is not simply provided to check feed rates etc, though this is performed and opportunities for CLO cost reduction are usually the first to be targeted.

What is clear however, is that there are significant differences between onboard analysis and lab analysis as well as differences between oil analysis suites.

As corrosive ear generates smaller wear particles which are not within the visibility of onboard magnetic PQ devices, these devices should only be used to warn of unexpected scuffing – therefore permanently installed in the drain line. Using the same technique onboard but offline for periodic sampling is often cited as being used to demonstrate that feed rate has not be “over optimised” to the extent that the oil film is being routinely disrupted and producing adhesive/scuffing wear debris. My view is that in reality this level of feed rate optimisation leaves no room for error and is in all probability a false economic approach in this application.

For lab analysis – there are the issues of immediacy for obvious reason but if your laboratory uses a sensible approach to dilution correction to normalise the effects of contamination by system oil, fuel, water and feed rate variability. Then it is perfectly reasonable to use such a test suite to help optimise feed rate in accordance with variations in Sulphur content and differences in CLO BN performance.

I would recommend to check that your lab based CDO analyses are subject to at least a system oil correction and I would also strongly recommend that a scavenge space cleaning regime is built into the schedule to ensure that each sample represents oil arriving via the liner and not simply that which has accumulated over the previous few days which will have no useful relevance to the operation at the time of sampling and thus weaken any diagnosis.

I would suggest that samples be drawn during steady state operation at a point approaching port which will allow the samples to be passed to the courier in the shortest time possible in order that your laboratory can get the results back to the ship in the shortest time thus increasing operational relevance to the task.


“It cannot be stated how much care must be taken when assessing scavenge drain oil …..
Unless some extensive form of dilution correction is undertaken based upon knowledge of the fuel oil, new and used system oil, feed rates and operational data collected from the engine at the time of sampling, use as a routine condition monitoring tool is limited to the measurement of significant changes issues such as high iron, water or BN change.”

CIMAC Used Engine Oil – User Interpretation Guide
Guidance Number 30 issued 2011

No need to open main bearings on Man Diesel Engines

Click to view SL2012-522 Main Bearing Inspection

Man Diesel now state clearly that bearing removal is not recommended as normal practice and therefore not recommended unless evidence based reason dictates.

This is a clear indication that best practice has shifted from a direct inspection methodology to a condition based approach.

This represents a shift in emphasis where the OEM clearly states that opening bearings without cause is likely to increase the risk of issue, either directly by the introduction of new sources of failure such as dirt or re-build issues, or by implication by reducing the support in terms of warrantee, where non recommended strip down may in the future invalidate terms.

Herein a video of the process for bearing removal courtesy of Marine Insight (Apologies for corrupted quality at the end! DS)

Can Classification Societies really align with Condition Monitoring?

Classification and Condition Monitoring

One of the things that seems unusual is that whilst approximately 10% of classed vessels have their planned maintenance systems recognised by their classification society. This allows the Chief Engineer to credit a number of items for survey at some convenient time, only about 10% of these use approved condition monitoring process which the Chief can use to avoid opening these assets purely for the purposes of satisfying the regulatory requirement.

What that means is that only 1% of ships use condition monitoring for the purposes of classification. It is suspected that a significant number of vessels successfully employ some form of condition monitoring on a regular basis and may even use condition as a foundation for their maintenance strategy but do not take up the opportunity to align these processes with their classification society and therefore must be performing unnecessary invasive surveys and in doing so increasing the risk to reliability.

Why is this?

Marine Machinery Condition Based Maintenance

The world of the marine engineer is changing and instead of maintaining machines best practice is to maintain reliability. What I mean by this is that the act of maintenance has traditionally been one based upon the performance of tasks at predetermined intervals. These would vary in scale from simple checks and cleaning to performing a full strip down for overhaul and component renewal. Therefore the required skill was to be able to understand how to perform these tasks and return the machine successfully  into service.As a result of improvements in design and a tendency to reduce the need for running repairs, there has been an increase in the use of throwaway components, e.g. sealed for life bearings. Coupled with the ever present need to operate at reduced  cost means that more often nowadays the engineer is tasked with developing strategies to understand and react to condition thus avoiding or extending scheduled intervals of intervention until necessary. This approach is broadly described as a risk based approach. The engineer is now not maintaining the machine but maintaining the reliability of the machine.

The question to be answered is whether the emerging technologies and practices  can be adequately implemented using staff who’s training is based upon traditional engineering principles when what is required is different. Not that engineers are not competent or sufficiently skilled to adapt, but whether the companies who employ them have developed and matured sufficiently to allow them to work in a different way.

Maintenance handbooks produced by manufacturers must by definition stipulate activities for every end user to reach an acceptable degree of reliability. This means that in the main most machines MUST be either over maintained or being maintained in a way that relieves  the manufacturer of any liability in the event of a failure within the period of guarantee. Even when machines are in service beyond the traditional period for which guarantees are in place, in the event of a failure sufficiently significant to invoke the need for a claims or loss adjustment exercise, the company in question will find itself at higher risk of penalty due to reduced cover.

This the employed skills, the company culture and the risk protection devices are misaligned when compared to industry best practice. It is easier to employ traditional and hence sub-optimal methods to maintain machines in the marine industry.